Effect of computed tomography of the appendix on treatment of patients
and use of hospital resources

Authors

Rao P, Rhea J, Novelline R, Mostafavi A, McCabe C.

Source

New England Journal of Medicine. 338:141-6. January
15, 1998.

Institution

Massachusetts General Hospital, Boston.

Support

General Electric Medical Systems

Background

The diagnosis of acute appendicitis is difficult. Many cases of undiagnosed
appendicitis and of unnecessary appendectomies occur each year. CT scanning,
in particular helical CT after Gastrografin instillation into the colon,
has been shown to be a very useful tool for the diagnosis of appendicitis.
This study was designed to examine the effect of appendiceal CT scanning
on overall hospital costs.

Methods

Patients

Patients were eligible for the study if they presented directly to the
emergency room (or were referred there) with suspected appendicitis and
if a surgeon decided to hospitalize them, based on history, physical examination
and labwork, for this diagnosis.

Intervention

Prior to appendiceal CT, the admitting surgeon estimated the likelihood
of appendicitis as definite, probable, equivocal or possible.

The patients then underwent focused helical appendiceal CT after instillation
of Gastrografin saline solution into the colon.

The scans were interpreted by one of three ER physicians as having a
likelihood for appendicitis of: definite, probable, equivocal, probably
not or definitely not. They were further classified as: appendicitis or
an alternative diagnosis or normal appendix without an alternative
diagnosis.

Analysis

Effect of CT on patient care

Final outcomes were determined by the results of surgery or by clinical
follow-up at least two months later for those patients who did not undergo
surgery.

Treatment plan prior to CT (admission for observation or urgent surgery)
was compared to actual treatment (discharge from the ER, admission for
observation, treatment for another condition, urgent appendectomy and other
surgery).

Effect of CT on use of hospital resources

A number of determinations and calculations were made to determine the
effect of CT on costs:

The total hospital cost of an unnecessary appendectomy (removal of a normal
appendix) was determined by retrospective analysis of the hospital's cost
database. The savings to be gained by avoiding an unnecessary appendectomy
was calculated as the total hospital cost of an unnecessary appendectomy
minus the emergency room costs prior to CT scanning.

It was assumed that each patient who would have been admitted for observation
but was able to be discharged based on CT scan results would have been
hospitalized for just one day of observation. Thus, the savings achieved
by CT scanning was calculated as the cost of a day of observation for suspected
appendicitis (based on the cost of one day of nursing care and hospital
room at the lowest level of illness severity).

The savings achieved by CT was calculated as the number of unnecessary
appendectomies avoided times the savings per appendectomy avoided, plus
the number of hospital admissions for observation avoided times the savings
per admission avoided. From this sum, the cost of 100 appendiceal CT scans
was subtracted to determine the overall cost savings from the use of CT
scanning. The cost of a CT scan of the pelvis without contrast was used
to estimate the cost of an appendiceal CT.

Results

100 consecutive patients were included in this study. No patients declined
participation.

Effect of CT on patient care

There were 53 surgically confirmed cases of appendicitis. The other
47 patients did not have appendicitis, based on clinical follow-up (41
patients), appendectomy with normal appendix (3 patients) and other surgery
(3 patients).

The appendiceal CT had a 98% sensitivity, specificity, positive and
negative predictive value and overall accuracy. There was one false positive
and one false negative CT scan.

CT scan was far more sensitive and specific than the pre-CT clinical
diagnosis. For example, among 23 patients in whom the clinical diagnosis
of appendicitis was rated "definite", there were 5 patients in whom it
was ruled out.

Author's discussion

According to the authors, had management been based on clinical evaluation
only, 13 patients would have had unnecessary appendectomies and 21 would
have had a needed appendectomy after a delay. Integrating the CT scan results
into management decisions, three patients had an unnecessary appendectomy
and none had a delay.

The authors feel that the cost savings they calculated were understated
for several reasons. First, they feel that some of the patients who would
have been hospitalized for observation would eventually have undergone
unneeded appendectomies. Second, they estimated the cost of observation
very conservatively. And third, they did not include other benefits from
improved diagnosis and treatment such as reduced disability.

They note, however, that expanded use of CT in patients in whom the
suspicion of appendicitis is lower than those studied here would decrease
the savings.

Editorial

In an accompanying editorial, Dr. Ian McColl (Guy's Hospital, London) notes
that the diagnosis of appendicitis remains difficult, with frequent false
positives and false negatives. Although ultrasound was thought to be a
promising technique, appendiceal CT is more sensitive and specific. Ultrasound
may still be more useful in children, since it is quicker, simpler and
does not require any exposure to radiation.

He notes that although CT is a very useful technique, overreliance on
technology should not be allowed to diminish clinical skills, which would
lead to more and more indiscriminate scanning. The costs related to CT
scanning will rise as more and more scans are performed.

Comment

In this study, the effect of appendiceal CT scanning on overall hospital
costs was studied. In patients who were felt to be at high risk of appendicitis,
CT scanning not only greatly improved diagnostic precision but also reduced
overall hospital resource use, since unnecessary appendectomies and unnecessary
delays in surgery were avoided.

I have one methodologic criticism of this study. The effect of CT scanning
on patient management was determined by comparing surgeons' plans before
CT scanning with their plans after the results of the scan were known.
However, knowledge that patients were to undergo CT scanning might have
influenced the surgeons' pre-scan assessments.

For example, a surgeon might be more likely to record "immediate surgery"
rather than "observation" as the plan if he or she knew that a CT scan
was about to be performed and that the final decision would be made after
that. This would increase the number of pre-scan assessments pointing to
surgery, and would increase the number of unnecessary appendectomies prevented
by CT scanning. We cannot automatically assume that surgeons who knew that
their patients were about to undergo a very precise diagnostic test would
necessarily make the same decisions for the purpose of the study as they
would have in caring for the patient in the absence of CT scanning.

A second point, noted by both the authors and the author of the editorial,
needs to be emphasized. The cost savings were determined in a population
at high risk for appendicitis; only patients who were felt to require either
urgent surgery or admission for observation were eligible for this study.
If the technique becomes more widespread and available, it will most certainly
be applied to a population at much lower risk. In a lower risk population,
the cost savings would be substantially lower and could easily turn into
a cost increase. If every patient who comes to the emergency room with
unexplained nausea and fever or vague abdominal pain is given the benefit
of an appendiceal CT scan, no money is likely to be saved. This doesn't
mean that the CT scan is less useful in a lower-risk population, only that
the cost-savings are likely to disappear.

This paper contributes more evidence to the notion that appendiceal
CT scanning is a better way to diagnose acute appendicitis. The paper's
focus is on cost reduction, however. I do not believe these results, in
terms of dollars saved per patient scanned, will be borne out in practice.

February 15, 1998

References

Reader Comments

Date: Thu, 05 Mar 1998
From: sachin dave <sdave@musom.marshall.edu>

I feel there is a possibility of observer bias more than what we realize.
Surgeons may not have performed a detailed clinical exam, knowing that
patients will undergo helical ct with gastrograffin anyways. Surgeons/ER
physicians should have been blinded to the fact that patients were undergoing
the study investigation.

Long term follow-up is not available. We do not know of the cost incurred
from a ruptured appendix that should have been removed, but was not because
of a negative ct scan (false negative).

I think we need a more well designed study. Clinical exam is still next
to gold standard (surgical specimen). Comparision should be made between
clinical exam and helical ct in a prospective manner.

I agree that the fact that surgeons were aware that patients were
to undergo CT scanning may have introduced bias into the decision-making
process.

The problem of false negatives causing increased costs that were
not accounted for is a potential one, but patients were followed up 2 months
after discharge. This would probably be long enough to catch most late
complications. -- mj

Date: Tue, 07 Apr 1998
From: "Dr. Zakko" <szakko@emirates.net.ae>

Dear sir

Both the article and the comment mentioned the use of CT and US for
the diagnosis of appendicitis.I would like to add further that labelled
WBC has been used for such application. First TC-WBC has been used. It
is highly specific, but it takes at least 90 min. to prepare and further
one hour to image. More recently An anti-bodies (fragments) labelled with
Tc-99m were used to label the white cells IN-VIVO and image in an hour.

It has already been approved by the FDA recently. I think now it would
be fair to note that Nuclear Medicine is all the time ignored. It is unfair!
or IS it lack of awareness?

I feel there is another advantage to helical scanning for appendicitis
in addition to the possible cost savings put forth in this article.
From the stand point of an emergency medicine resident operating in an
academic center, scanning can accelerate the diagnosis in cases in which
appendicitis is high on the differential, but the exam and lab findings
are equivocal (as they often are). The time involved in having these patients
evaluated by multiple levels of surgeons, at various points in their training,
not to mention OB-Gyne consults frequently performed at the behest of surgeons
in female patients, can lead to hours upon hours in the Emergency Room
before a disposition is achieved. In my experience, surgery almost
inevitably requests a CT rather than taking the patient straight to the
OR anyway, so we often order a CT in equivocal cases and call surgery based
on the results.

I believe this will become more standard in the future, and perhaps
in 5-10 years appendicitis will be, if not an emergency medicine disease,
a diagnosis made or ruled out reliably by emergency physicians rather than
surgeons.

Don't forget, the first walkin centers were started in chicago, just
across the street from the ER, by combining time/cost considerations, without
compromising patient care. Sounds like the time has come for CT to be the
dx method of choice for appendectomy.